gas notes - pain management Flashcards
What typically triggers acute pain?
Nocioception due to tissue damage
An example is stepping on a Lego brick.
How long does chronic pain persist after the initial insult?
More than three months
What is hyperalgesia?
Pain out of proportion to a stimulus
What does allodynia refer to?
Painful interpretation of non-painful stimuli
Define neuropathic pain.
Pain originating from conducting nerve damage
What is phantom limb pain?
Pain after amputation of a limb
Why is chronic pain more difficult to treat than acute pain?
It typically originates from harder-to-target levels above transduction, including within the brain itself.
What is paracetamol?
An effective and relatively-harmless analgesic that should feature in (almost) every pain management plan
Paracetamol is widely used due to its safety profile and efficacy in managing pain.
What do NSAIDs do?
Block the formation of inflammatory prostaglandins by inhibiting cyclo-oxygenase enzymes (COX)
NSAIDs can lead to issues such as renal impairment, GIT ulceration, ischaemic heart disease, and bronchospasm.
What is the role of opioids in pain management?
Heavy lifting in acute pain but limited role in chronic pain management
Opioids are more effective for short-term pain relief rather than long-term management.
What is tramadol?
A hybrid opioid and SSRI that increases descending inhibition
Tramadol provides good analgesia for most patients but should be avoided in older patients due to the risk of delirium.
What is tapentadol?
A metabolite of tramadol that causes less delirium and is more expensive
Tapentadol is often used when tramadol is not suitable.
What is buprenorphine?
A ‘partial agonist’ at μ opioid receptors that has less respiratory depression and equal analgesia
Buprenorphine can be safely co-prescribed with other opioids at normal doses.
What is unique about oxycodone?
Has a pretty fast onset and is excellent for severe acute pain
Oxycodone has immense potential for abuse, requiring careful monitoring.
What are the characteristics of morphine?
The original opiate, not commonly used today, very nauseating, and accumulates toxic metabolites in renal failure
An antiemetic is often co-prescribed with morphine to manage its nausea.
What is fentanyl?
Very fast and short-lived with perfect safety in renal failure
Fentanyl is often used in acute settings due to its rapid action.
Is there a role for codeine in modern pain management?
No, there is no role for codeine in modern pain management
Codeine has largely been replaced by more effective analgesics.
What are the primary adverse effects of opioids?
Nausea, sedation, and dose-dependent respiratory depression
These effects highlight the importance of careful dosing and monitoring in opioid therapy.
What formulations do most opioids come in?
Slow-release and immediate-release formulations
The choice of formulation can depend on patient needs and local policies.
try to use the same drug for both
list some adjuvants
Ketamine
Pregabalin (and gabapentin)
Clonidine
Tricyclic antidepressants
SNRIs
What are the three common local anaesthetics in Australia?
Lignocaine, Bupivacaine, Ropivacaine
Lignocaine is primarily used in day-to-day practice, while Bupivacaine and Ropivacaine are used in more specific contexts.
What concentrations are available for Lignocaine?
1% or 2%
Lignocaine is often pre-mixed with adrenaline.
Which local anaesthetic is popular for spinal blocks?
Bupivacaine
Bupivacaine is available in concentrations of 0.25% or 0.5% and is sometimes pre-mixed with adrenaline.
What concentrations are available for Ropivacaine?
0.2%, 0.75%, and 1%
Ropivacaine is popular for regional blocks and is sometimes pre-mixed with adrenaline.
What is Local Anaesthetic Systemic Toxicity (LAST) characterized by?
Arrhythmia, seizure, and coma in severe cases
LAST is almost always caused by accidental intravenous injection.
True or False: Ropivacaine is used primarily for spinal blocks.
False
Ropivacaine is popular for regional blocks, while Bupivacaine is used for spinal blocks.
What should you always do before injecting local anaesthetic to avoid LAST?
Draw back
Always draw back before injection to check for accidental intravenous injection.
What is the primary aim of regional anaesthesia?
To bathe a single nerve (or plexus) in local anaesthetic to prevent nocioceptive transmission
This technique is used to block pain signals from specific areas of the body.
What guidance method do most anaesthetists use for regional anaesthesia?
Ultrasound guidance
Ultrasound allows for better visualization of nerves and improves the accuracy of anaesthetic delivery.
What is a major benefit of regional anaesthesia?
It is an excellent opioid-sparing technique
This means it can reduce the need for opioids during and after surgery.
What is a common side effect of local anaesthetic in regional anaesthesia?
Motor blockade
Local anaesthetic not only blocks pain but can also affect muscle movement.
What is intravenous regional anaesthesia?
An old-school technique where a limb is isolated from circulation by tourniquet and flooded with intravenous local anaesthetic
This method was historically used for procedures on the limbs.
What is Bier’s block?
A famous example of intravenous regional anaesthesia
Named after Heinrich Bier, this technique involves a tourniquet and local anaesthetic administration.
What risk is associated with intravenous regional anaesthesia?
High risk of toxicity
Due to the concentration of local anaesthetic in a confined area, there is a significant risk of systemic absorption leading to toxicity.
Why is intravenous regional anaesthesia becoming redundant?
Due to the wide availability of ultrasonography
Ultrasonography provides safer and more effective alternatives for nerve blocks.
What is neuraxial anaesthesia?
A type of local anaesthesia applied to the spine that numbs the entire lower half of the body with a small dose of anaesthetic
It is risky, invasive, time-consuming, and difficult.
When are neuraxial techniques relevant?
They are relevant for surgery below the umbilicus
Particularly useful for avoiding general anaesthesia in high-risk patients.
What are the benefits of neuraxial anaesthesia in high-risk patients?
Avoids the need for large doses of opioids and hypnotics
This can reduce the risk of complications associated with general anaesthesia.
At which vertebral level does the spinal cord typically terminate in adults?
L2
Below L2, there is a collection of nerve roots and cerebrospinal fluid (CSF) known as the lumbar cistern.
Where should the needle be aimed when performing a neuraxial block?
At the L3/4 interspace or lower
This helps to avoid damaging the spinal cord.
What is a spinal block?
A single shot of local anaesthetic injected into the lumbar cistern
Sometimes mixed with other agents and cannot be ‘topped up’ once they wear off.
List the structures the needle passes through to reach the subarachnoid space.
- Skin
- Subcutaneous fat
- Supraspinous ligament
- Interspinous ligament
- Ligamentum flavum
- Epidural space
- Dura mater
- Arachnoid mater
- Lumbar cistern
This pathway is crucial for the administration of spinal anaesthesia.
What is the density characteristic of local anaesthetic compared to cerebrospinal fluid?
Local anaesthetic is slightly less dense than cerebrospinal fluid (hypobaric)
It can be made ‘heavy’ (hyperbaric) by mixing with dextrose.
What effect does a heavy mixture of local anaesthetic have when the patient lies on their side?
Produces a unilateral block
This is due to the heavy mixture sinking.
What is an epidural block?
A technique where a flexible catheter is threaded into the epidural space
Local anaesthetic is periodically injected to anaesthetise the nerve roots.
What are epidurals best suited for?
Long-lasting pain like labour and delivery.
True or False: Neuraxial blocks are generally considered unsafe and poorly tolerated.
False
Neuraxial blocks are generally safe and well-tolerated.
What are the main risks associated with neuraxial blocks?
- Failure (especially epidurals)
- Headache
- Bleeding
- Infection
- Neurological injury
- High block
These risks should be communicated to patients before the procedure.
What are some contraindications for neuraxial blocks?
- Patient refusal
- Impaired coagulation
- Raised ICP
- Uncooperative patient
- Underlying neurological or spinal disease
- Fixed cardiac output
- Shock
What is a ‘high block’ in the context of local anaesthetic administration?
A phenomenon where local anaesthetic migrates above T4, causing profound bradycardia, hypotension, and diaphragmatic paralysis.
What is the life-threatening condition that can occur if local anaesthetic reaches the cranium?
‘Total spinal’ anaesthetic.
